In 1972, Prof. Bhatnagar returned to India to establish a unique island solar observatory in the middle of Lake Fatehsagar in Udaipur under the aegis of the Vedhshala, Ahmedabad.
Due to his efforts, the solar observatory was taken over by the Department of Space in December 1981 for its speedy growth, and was affiliated to the Physical Research Laboratory, Ahmedabad.
This was an attempt by Indian Scientists to pin down the exact diameter of the sun-which today still remains unknown, by precisely measuring the sun's shadow cast on the earth.
Separately, a pair of IAF MiG-25 fighters were fitted with equipment to photograph the outer solar corona and also the dust rings around it, in the darkest, clearest possible sky.
In 1996, Prof. Bhatnagar started a novel project called SUCHE (Swatch, Healthy, Urban, Clean and Hygienic Environment) Abhiyan in several localities of Udaipur under ASTHA Sansthan for solid waste management through public participation.